It's a very valid point - it doesn't take a genius to figure out competition drives development, while having a market monopoly affords you a great position of "extortion" in regards to your customers (developers). If there was only one solution from only one company, it would literally be their way - and that's it.
Then again, this is why we first develop web standards or markup languages (e.g. HTML, XHTML, XML) in the first place ;)
Take a look at http://quetzalcoatal.blogspot.com/2013/02/why-software-monoc.... The author points out how GCC's monopoly, though open source, forces clang to copy its implementation quirks almost exactly, because it's been the de-facto standard for years. Open-source doesn't automatically make the problem go away.